It is an Art to be able to build a stack which is statisticaly open for the largest number of Tetriminos..
WEll, yeah... that's obvious. But barring that I will ALWAYS take the tetris when playing with a memoryless randomizer. I learned that lesson the hard way. Especially since many games with a memoryless randomizer have zero lock delay, it's more important to drop the stack size by 4 as soon as possible. I will take the tetris, and if a second I doesn't showup quickly, stuff an L or J in the hole, and work my way back down and reset my tetris setup. and unstable and low stack is better than a stable and high one when there's no lock delay.
You should be expecting one soon if you haven't seen one in the last 4 pieces. I can't count the number of times while playing a TGM game i have a choice of where to place a piece and end up thinking "hmm i haven't seen a O for a while, I better make some space for it" and sure enough, one shows up within 2 pieces. You are just used to the draughts that tend to happen in memoryless.